Environmental Statement - Maersk Oil

Balloch Field Development Environmental Statement
Section 6 Accidental Spills
6. ACCIDENTAL SPILLS
As part of the EIA process, it is necessary to consider the effects of an unplanned hydrocarbon spill on
the environment. DECC issued new advice on their requirements relating to oil pollution emergency
preparedness on 23 rd December 2010 (updated 21 st July 2011 and 20 th September 2011) (DECC,
2010). This section aims to satisfy these requirements.
In the event of a hydrocarbon spill at the Balloch field, there is the potential to impact the waters and
coastline of the North Sea. Oil fate modelling has been undertaken using the SINTEF Oil Spill
Contingency and Response (OSCAR) model which has significant scientific research and validation
(Reed et al., 1995; Reed et al., 1996; Johansen et al., 2001).
OSCAR calculates and records the distribution (as mass and concentrations) of contaminants on the
water surface, on shorelines, in the water column and in sediments. For subsurface releases (e.g.
subsea blowouts or pipeline leaks), the near‐field part of the simulation is conducted with a multi‐
component integral plume model that is embedded in the OSCAR model. The near‐field model
accounts for the buoyancy effects of oil and gas as well as effects of ambient stratification and cross‐
flow on the dilution and rise time of the plume. The model uses three‐dimensional currents and two‐
dimensional winds to predict the movement of oil and incorporates an oil properties database that
supplies physical, chemical and biological parameters including evaporation data, emulsification,
sediment partitioning and decay processes. The version of OSCAR used was that contained within the
Marine Environmental Modelling Workbench Version 6.1.
Three hydrocarbon release scenarios are presented; these are:
Uncontrolled well blowout from a subsea release;
Uncontrolled well blowout from a surface release for the first 2 days, followed by a
continuation of the release subsea. This scenario represents a blowout that occurs initially
through the semi‐submersible drill rig;
Instantaneous release of the diesel inventory from the drill rig.
A blowout is defined as an incident where formation fluid flows out of the well or between formation
layers after all the predefined technical well barriers have failed.
For each spill scenario, both stochastic and deterministic analyses were carried out as per the DECC
guidance.
6.1. OIL SPILL REGULATIONS AND RISK
6.1.1. REGULATORY CONTROL ON THE UKCS
The key regulatory drivers that will assist in reducing the possible occurrence of oil or chemical spills
are as follows:
The Merchant Shipping (Oil Pollution Preparedness, Response and Co‐operation Convention)
Regulations 1998;
The International Convention on Oil Pollution, Preparedness, Response and Co‐operation (OPRC),
which has been ratified by the UK, requires the UK Government to ensure that operators have a
formally approved Oil Pollution Emergency Plan (OPEP) in place for each offshore operation or
agreed grouping of facilities;
The Offshore Installations (Emergency Pollution Control) Regulations 2002 give the Government
the power to intervene in the event of an incident involving an offshore installation where there
is, or may be, a risk of significant pollution, or where an operator has failed to implement proper
control and preventative measures. These regulations apply to chemical and oil spills;
The EC Directive 2004/35 on Environmental Liability with Regard to the Prevention and
Remedying of Environmental Damage enforces strict liability for prevention and remediation of
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